It has long been known that silicon, the base material from which MOSFETs are made, has piezoresistive properties that are of interest in the field of sensors.
Also known, e.g. from European patent EP-B-0 040 795, is a semiconductor sensor comprising an odd number of complementary metal oxide semiconductor (CMOS) inverters disposed in a zone which is sensitive to pressure, the inverters being inter connected to form a pressure sensitive ring oscillator. The frequency of the oscillator obtained in this way is directly related to the stress to which the semiconductor devices are subjected under the effect of pressure.
An object of the invention is thus to provide a semi conductor sensor having very good sensitivity while maintaining a relatively low cost price. Another object is to eliminate sensor drift under the effect of temperature and to improve the yield of the manufacturing process by reducing the number of rejects.